Roll assembly for use in calenders and the like

Abstract

The roll assembly of a calender has at least one roll with a deformable shell which surrounds a rigid carrier and whose end portions surround discrete antifriction bearings. The intermediate portion of the shell surrounds one or more rows of hydrostatic supporting elements which can be acted upon by adjustable fluid-operated motors to change the shape of the intermediate portion in a plane including the axes of the one roll and the neighboring roll as well as at right angles to such plane. Stresses which are applied to the bearings for the end portions of the shell are monitored by several sensors which transmit signals to a control system to regulate the deformation of the shell in such a way that the stresses upon the bearings are minimized or reduced to zero. This enables the intermediate portion of the shell to undergo deformation which is best suited for optimum treatment of the material passing through the nip of the one roll and the neighboring roll.

We claim: 
     
       1. A roll assembly, particularly a calender, comprising a first roll rotatable about a first axis; a second roll rotatable about a second axis which is parallel to said first axis, said second roll comprising a flexible elongated cylindrical shell defining with the first roll an elongated nip and having an internal surface, an intermediate portion and first and second end portions, a rigid carrier surrounded by said shell, first and second bearings respectively interposed between said carrier and the first and second end portions of said shell, and signal generating first and second sensor means for monitoring the stresses which are applied to said first and second bearings in a plane including said axes and intersecting said nip, particularly when a web of material which is being treated by the roll assembly passes through said nip; and means for counteracting said stresses, includng at least one row of supporting elements installed in said shell between said first and second end portions and surrounded by the corresponding parts of said intermediate portion, at least one adjustable motor installed between each of said supporting elements and said carrier and arranged to urge the respective supporting element toward the internal surface of said shell to thereby select the force with which the corresponding part of said intermediate portion is urged toward the first roll, and control means responsive to the signals from said sensor means and operative to adjust said motors so as to minimize or eliminate the stresses to which said bearing means are subjected by the respective end portions of said shell. 
     
     
       2. The assembly of claim 1, wherein said bearings include antifriction bearings. 
     
     
       3. The assembly of claim 1, wherein said supporting elements are hydrostatic supporting elements. 
     
     
       4. The assembly of claim 1, further comprising means for transmitting to said control means additional signals for adjustment of said motors as a function of at least one variable parameter. 
     
     
       5. The assembly of claim 1, wherein each of said sensor means comprises two discrete sensors disposed in the region of said plane and substantially diametically opposite each other with reference to the axis of said second roll. 
     
     
       6. The assembly of claim 1, wherein each of said bearings includes an antifriction bearing having an inner race surrounding said carrier, said sensor means being installed between said carrier and the respective inner races. 
     
     
       7. The assembly of claim 6, wherein at least one of said sensor means is recessed into said carrier. 
     
     
       8. The assembly of claim 6, wherein said carrier has a peripheral surface provided with flats and said sensor means are adjacent to such flats. 
     
     
       9. The assembly of claim 6, wherein said second roll further comprises a sleeve interposed between each of said inner races and said carrier, said sensor means being disposed within the confines of said sleeves. 
     
     
       10. The assembly of claim 9, wherein said shell is rotatable relative to said sleeves. 
     
     
       11. The assembly of claim 9, wherein said sensor means are recessed into said sleeves. 
     
     
       12. The assembly of claim 9, wherein said sensor means are recessed into said carrier. 
     
     
       13. The assembly of claim 1, wherein said sensor means are force transducers. 
     
     
       14. The assembly of claim 1, wherein said sensor means are pressure transducers. 
     
     
       15. The assembly of claim 1, wherein said sensor means are displacement transducers. 
     
     
       16. The assembly of claim 1, wherein said sensor means are distance transducers. 
     
     
       17. The assembly of claim 1, wherein each of said bearings include two portions one of which surrounds the other with play. 
     
     
       18. The assembly of claim 1, wherein said counteracting means further comprises additional supporting elements angularly offset with reference to the supporting elements of said row and at least one additional adjustable motor for each of said additional supporting elements, said second roll further comprising additional first and second sensor means disposed in the regions of the respective bearings and arranged to generate signals denoting the magnitude of additional stresses acting upon the respective bearings at right angles to said plane, said control means being operative to adjust at least said additional supporting elements so as to minimize or eliminate said additional stresses. 
     
     
       19. The assembly of claim 1, wherein at least one of said rolls has a viscoelastic outer layer which contacts the external surface of the other roll in the absence of any material in said nip and further comprising signal generating means for monitoring the temperature of said outer layer at a plurality of locations which are spaced apart from one another as considered in the longitudinal direction of said intermediate portion, said control means being arranged to adjust said motors in dependency on the characteristics of the temperature-denoting signals at the respective locations. 
     
     
       20. The assembly of claim 1, wherein said first roller is disposed at a level above said second roller and further comprising a third roller at least substantially identical with said second roller and disposed at a level above said first roller, and means for biasing said third roller downwardly toward said first roller. 
     
     
       21. The assembly of claim 20, further comprising at least one additional roller interposed between said first roller and one of said second and third rollers. 
     
     
       22. The assembly of claim 1, further comprising means for moving said carrier nearer to and further away from the axis of said first roller. 
     
     
       23. The assembly of claim 22, wherein the axis of said first roller is a fixed axis and said moving means comprises first and second levers pivotable about fixed axes and supporting said carrier adjacent to the respective end portions of said shell and fluid-operated motor means for pivoting said levers. 
     
     
       24. The assembly of claim 22, wherein said moving means includes means for biasing said shell against said first roll. 
     
     
       25. The assembly of claim 1, wherein the axes of said rolls are disposed at different levels.